A motor vehicle is fitted, in a known manner, with a plurality of wheels, each having a wheel rim and a tire mounted on said wheel rim. Nowadays, it is also known to mount a sensor device in each wheel, in particular to measure the pressure inside the corresponding tire. Such a sensor device may, for example, be mounted on an inflation valve of the wheel rim or be attached directly to the inside wall of the tire.
The sensor device sends the values that it measures over a radio link to a control unit of the vehicle, known to the person skilled in the art as an electronic control unit (ECU). This control unit of the vehicle uses these values to assist the driver when driving the vehicle. Thus for example, the control unit of the vehicle warns the driver if the pressure in one of the tires drops, in order to prevent a potential puncture.
When the vehicle is moving, the sensor device is subjected to significant acceleration, the value of which is for example several hundreds of g, g being the acceleration constant (g=9.81 m·s2). Consequently, it is not uncommon for the sensor device to become detached and to cease working correctly, preventing the electronic control unit of the vehicle from detecting a pressure drop in the tire, which is a first drawback. Furthermore, detachment of the sensor device may damage the tire, which is a second drawback.
In order to at least partially overcome this drawback, a solution described in document FR 2 874 086 discloses a device for detecting detachment of a sensor device. This method uses the speed of the vehicle and the acceleration of the sensor device to determine a correlation coefficient, the value of which depends only on the distance between the sensor device and the center of the wheel. However, the speed of the wheels may differ significantly from the speed of the vehicle, for example in the event of skidding, and the speed of the wheels may differ from one another, for example on bends and in particular tight bends. Consequently, this method provides an erroneous estimate of the distance between each sensor device and the center of the wheel on which it is mounted, which may prevent detection of the detachment of a sensor device, representing a significant drawback.